Non-contact heater and method for non-contact heating of a substrate for material deposition

ABSTRACT

A heater for the non-contact heating of an object, such as a substrate for material deposition, includes a housing defining a deposition cavity and a source of radiation outside the deposition cavity. A reflector is optically coupled to the source of radiation to collect the radiation and to focus it on the radiation path. The reflector may have different shapes. If, for example, the reflector is an ellipsoidal reflector, the source of radiation then is mounted in a first focus, the substrate is located in the other focus, and the radiation path is positioned on the main focal axis of the ellipsoidal reflector. The radiation from the source of radiation is delivered to the substrate inside the deposition cavity through a radiation path(s) formed in the housing wall to heat the substrate to the temperature T s , so that T 1 &lt;T s &lt;T 2 , where T 1  is the temperature of the housing wall, while T 2  is the effective temperature of the source of radiation.

FIELD OF THE INVENTION

The present invention relates to the non-contact heating of an object.The present invention is directed particularly to the heating of asubstrate for thin film deposition in the absence of convective heating.

More particularly, the present invention relates to a system and methodfor the non-contact heating of a substrate positioned in a depositioncavity by optical radiation emanating from a radiation source locatedoutside the walls of the deposition cavity in order to reach an optimalsubstrate temperature for material deposition.

BACKGROUND OF THE INVENTION

Non-contact (irradiative) heating is needed in the deposition of thinfilms onto a moving substrate in the absence of convective (gas)heating. It is customary to employ a cavity-type heater where asubstrate is disposed in the cavity while the walls of the cavity-typeheater are heated to a predetermined temperature T₁. In an ideal cavity,due to radiation exchange, the substrate may reach a temperature T_(s)which is close to the temperature of the cavity walls, i.e., (T_(s)≈T₁).The temperature T_(s) of the heated substrate in the ideal cavity istheoretically uniform over the surface of the substrate and is stable.

In reality, however, the cavity walls have at least one opening formedtherethrough to allow a deposition flux generated at the remote sourceof material into the cavity to reach the substrate for materialdeposition thereon.

Due to the presence of the opening in the walls of the cavity, a portionof the thermal energy of the substrate escapes from the cavity, thuscausing a decrease of the substrate temperature T_(s) below thetemperature T₁ of the walls of the cavity (T_(s)<T₁).

In a non-ideal cavity, the temperature of the substrate will always belower than the temperature of the walls. This causes unwanted obstaclesin the deposition of high quality films of multi-component materials.Specifically, in the deposition of crystalline epitaxially grown filmsof a material, the surface of growth; e.g., substrate surface, must beheated to an optimal temperature that is close to but less than thetemperature of decomposition T_(d) of the material (T_(d)≈T_(s)).

Thus, since T_(s)<T₁ and T_(d)≈T_(s), the wall temperature T₁ is higherthan the decomposition temperature T_(d) (T₁>T_(d)). Under thiscondition, a fraction of the material passing into the cavity with thedeposition flux (and unavoidably reaching the cavity walls) willdecompose along with the material reaching the substrate. There-evaporation of the material components from the walls will change thecomposition of the film growing on the substrate and, as a result, maydegrade its properties.

Another technique customarily used to heat a substrate is radiationheating wherein a radiation from a remote source having an effectivetemperature T₂>>T_(s), is directed onto the substrate. A laser or quartzhalogen lamp may be used as the source of the radiation.Disadvantageously, the laser radiation of sufficient power (˜0.5 kW forthe substrates of reasonably large area ˜10 cm²) is relatively expensiveto produce, and it is difficult to attain a uniform and stabletemperature T_(s) over the substrate area in the open heaterarrangement.

The heater arrangements using lamps, in addition to high cost, requirethe lamps to be protected against the unwanted deposit of material. Tolower the material deposited on the lamp surface, the lamps are usuallydistanced from the substrate, which requires radiation delivery optics,including focusing elements, mirrors, etc., resulting in furtherdegradation of the uniformity and stability of the substratetemperature.

A technique for non-contact heating of a substrate for materialdeposition which provides stable and uniform heating of the substratesurface to a temperature satisfying the conditions required formulti-component films deposition is therefore needed in the industry.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a non-contact heaterand a technique for the stable and uniform non-contact heating of asubstrate surface to a temperature optimal for multi-component materialdeposition.

It is another object of the present invention to provide a non-contactheater built of a housing (where an object to be heated is positioned)and of a source of directed radiation positioned outside the housing.The radiation emanating from the source of directed radiation isdelivered to the substrate through a small radiation path formed in thewall of the housing.

It is also an object of the present invention to provide a non-contactheater containing a cavity heater and a reflector housing forming anellipsoidal reflector attached to the wall of the cavity heater. In sucha heater, a source of radiation is positioned in the first focus of theellipsoidal reflector, while the object to be heated is located inproximity to the second focus. The radiation emanating from the sourceof radiation is delivered therefrom to the object through the radiationpath formed in the wall of the cavity heater. The radiation path islocated on the main focal axis of the ellipsoidal reflector whichconnects the first and the second focuses thereof.

It is a further object of the present invention to provide a cavityheater with an additional source of radiation mounted remotely andisolated from the deposition cavity, in which the additional source ofradiation is radiatively coupled to the substrate to attain a substratetemperature T_(s), such that T₁<T_(s)<T₂, where T₁ is the temperature ofthe walls of the deposition cavity, and T₂ is the effective temperatureof the source of radiation.

It is an additional object of the present invention to provide atechnique for the non-contact heating of a substrate for materialdeposition in which a substrate is positioned in a deposition cavity,where the walls are heated to a predefined temperature, and a depositionflux generated by a remote deposition source reaches the substratethrough a deposition opening formed in the cavity walls. Further,additional radiation is delivered to the substrate from a remote sourceof optical radiation to stably and uniformly heat the substrate surfaceto a temperature exceeding the temperature of the walls of the cavityand below the effective temperature of the source of radiation.

It is still a further object of the present invention to provide anon-contact heater for a substrate and a technique for non-contacttemperature measurement of the heated substrate using a spatiallyselective non-contact temperature sensor which is placed in the plane ofthe substrate image (created by radiation capturing optics) and which issized to match the size of the image of the substrate area chosen to beused for temperature sensing.

The present invention provides for a non-contact heater system forheating an object, for example, a substrate for material deposition. Thesystem includes a housing forming a deposition cavity defined by housingwalls in which a flux opening and at least one radiation path areformed. The substrate is positioned inside the deposition cavity, whilethe flux opening is aligned with the deposition flux emanating from adeposition source disposed remotely from the deposition cavity in orderto couple the deposition flux to the substrate.

The non-contact heater further includes a reflector for directing theradiation to the radiation path. The reflector may be arranged inseveral fashions. For example, it may be a planar mirror positionedbehind the radiation source, or have a shape of rotational paraboloid,parabolic cylinder, etc. The reflector also may be shaped as anellipsoidal reflector attached to the housing wall. The source ofradiation is then positioned in a focus of the ellipsoidal reflector andradiatively coupled to the substrate in the deposition cavity. Thesubstrate is positioned in proximity to the other focus of theellipsoidal reflector. Preferably, for heating an extended substrate,the reflector is shaped as an elliptical cylinder.

The source of radiation is preferably optical in nature and is mountedoutside the deposition cavity in the ellipsoidal reflector. Theradiation source generates radiation which is delivered to the substrateto heat the substrate to a temperature above the temperature (T₁) of thehousing wall of the deposition cavity but below the effectivetemperature (T₂) of the source of radiation. Preferably, a pair ofradiation sources are positioned outside the deposition cavity, fromwhich the radiation is coupled to the substrate through radiation pathsformed in the housing wall. Each radiation path is located at the mainfocal axis of a respective ellipsoidal reflector between the focusesthereof.

The sources of radiation may include quartz halogen lamps positioned inellipsoidal reflectors attached to the walls of the deposition cavityand in alignment with the radiation paths formed in the walls.

It is of particular importance that the source of radiation ispreferably positioned at one focus of the ellipsoidal reflector, whilethe substrate is positioned in proximity to the other focus of theellipsoidal reflector, and that the main axis of the ellipsoidalreflector extends through the radiation path formed in the housing wall.This arrangement allows for delivery of the radiation from the source ofradiation to the substrate in the most effective manner with no need forfiber optics or other radiation delivery optics. The radiation sourcesare positioned off the axis of the deposition flux emanating from thedeposition source and entering the deposition cavity in order to protectthe sources of radiation from material deposition thereon.

The housing wall of the deposition cavity can be heated by heatingelements such as, for example, a heater winding attached to the housingwall inside or outside the deposition cavity.

It is important to maintain the radiation paths, made in the housingwall of the deposition cavity, clear and optically transparent. For thispurpose, deposition screens may be mounted inside the deposition cavityto prevent deposition of material on the radiation paths.

Additionally, the present invention is directed to a method for heatinga substrate for material deposition which includes the steps of:

-   -   a) mounting a substrate in a deposition cavity defined by a        housing wall,    -   b) heating the housing wall to a temperature T₁,    -   c) forming a flux opening and a radiation path in the housing        wall of the deposition cavity,    -   d) mounting radiation sources outside the deposition cavity. If        the arrangement uses the ellipsoidal reflectors attached to the        housing walls, then each source of radiation is mounted in one        focus of the respective ellipsoidal reflector, while the        substrate is located in the other focus (or in proximity of the        other focus) thereof, and while the main focal axis of the        ellipsoidal reflector extends through the radiation path formed        in the housing wall; and,    -   e) delivering the radiation emanating from the radiation sources        to the substrate through the radiation paths formed in the        housing wall of the deposition cavity to heat the substrate to a        temperature T_(s), where T_(s) is above the temperature of the        housing wall but below the effective temperature of the        radiation source.

The method further includes the step of measuring the substratetemperature in a unique manner, including the steps of:

-   -   a) choosing an area S on the substrate,    -   b) forming one or more holes in the housing wall, which are in        direct communication with the area S on the substrate,    -   c) positioning a lens (radiation capturing optics) against each        of the holes to create an image of the area S in a predetermined        plane outside the deposition cavity, and,    -   d) positioning a radiation sensor in the predetermined plane and        in alignment with the created image to sense and measure the        radiation emanating from the area S. It is of great importance        that the radiation sensor be sized to match the dimensions of        the area S on the substrate.

These features and advantages of the present invention will be fullyunderstood and appreciated from the following Figures outlined in theDetailed Description of the Accompanying Drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic representation of a non-contact heater of thepresent invention with a pair of elliptical cylinder reflectorsembedding radiation sources attached to the deposition cavity;

FIG. 2 is an alternative embodiment of the non-contact heater of thepresent invention with flat Thermocoax™ coils heating the walls of thedeposition cavity;

FIG. 3 illustrates an example of the Thermocoax™ winding having anexemplary Thermocoax™ bending configuration;

FIG. 4 is a prospective view of the non-contact heater of the presentinvention including the ellipsoidal cylinder reflector attached to thedeposition cavity adapted for the tape-like substrate;

FIG. 5 shows schematically the non-contact heater of the presentinvention with the reflector including a planar mirror;

FIG. 6 is a prospective view of the non-contact heater of the presentinvention with parabolic cylinder reflector;

FIG. 7 is a schematic representation of a technique for non-contactmeasurement of the substrate temperature employed in the non-contactheater of the present invention; and

FIG. 8 shows schematically the non-contact heater of the presentinvention adapted for the tape-like substrate with a non-contactmeasurement arrangement.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The principles of the present inventive concept are applicable to thenon-contact heating of any object, however, for purposes of a betterunderstanding of the present invention, and as one of the examples ofthe particular application of the subject non-contact heating technique,the following description is directed primarily to the non-contactheating of a substrate for material deposition. As such, referring toFIGS. 1 and 2, a non-contact heater 10 includes a housing which has adeposition cavity 12 defined by a housing wall (or a cavity wall) 14, inwhich a deposition opening 16 and a pair of radiation paths 18 and 20are formed. An object to be heated; e.g., a substrate 22, is mountedinternal the deposition cavity 12 at a predetermined position therein. Adeposition source 24 is mounted remotely from the deposition cavity 12to generate a deposition flux 26, which enters the deposition cavity 12through the deposition opening 16 for coating the substrate 22 to formcrystalline films on the surface of the substrate 22. Sources ofradiation 28 and 30 are positioned remote from the deposition cavity togenerate optical radiation impinging on the surface of the substrate inorder to uniformly and stably heat the substrate surface to an optimaltemperature for multi-component material deposition.

Cylindrical ellipsoid reflectors 32 and 34 are coupled to the walls 14of the deposition cavity 12 in precise registration with radiation paths18 and 20, respectively. The sources of radiation 28 and 30 are locatedat the first focus 36 of the respective cylindrical ellipsoid reflectors32 and 34. The cylindrical ellipsoidally-shaped reflectors 32 and 34provide coupling of the sources of radiation 28 and 30 to the substrate22. The inner surfaces of the reflectors 32 and 34 are coated with goldor a similar reflective coating which is substantially inert to preventoxidation and degradation of its reflective qualities. The bodies of thecylindrical ellipsoid reflectors 32 and 34 are generally cooled throughwater cooling or a similar technique.

The radiation paths 18 and 20 define optically transmissive windowsformed in the walls 14. By locating the sources of radiation 28 and 30in the first focus 36 of the cylindrical ellipsoid reflectors 32 and 34,and by positioning the substrate near a second focus 38 of eachreflector, the coupling between the radiation emanating from the sources28 and 30 and the substrate is provided in the most optimal fashionthrough the radiation paths 18, 20, which are located on the main focalaxis 39 of the respective ellipsoidal reflector.

Preferably, the radiation sources 28 and 30 are quartz halogen lampswhich may, preferably, have a diameter of 8 mm. The radiation sources28, 30 are located along the main focal axis of each reflector,preferably approximately 10 mm away from the nearest surface thereof. Asshown in FIG. 1, the other foci 38 of the reflectors 32 and 34,respectively, are located between the substrate 22 and the ellipsoidfoci 36, or coincide with the substrate 22. This mutual dispositionbetween the radiation sources and the substrate minimizes the size ofthe radiation paths 18 and 20, thus improving the overall effectivity ofthe heater.

In order to keep the radiation paths 18 and 20 optically transmissive,which is necessary for direct radiative communication between thesources of radiation 28, 30 and the substrate 22, and to prevent themfrom accumulating the material conveyed into the deposition cavity 12with the deposition flux 26, a deposition screen 40 may be mounted inproximity to the radiation paths 18 and 20.

The walls 14 of the deposition cavity 12 are heated to a temperature T₁by a heater which may be, for example, in the form of curved Thermocoax™coils attached to the walls 14 inside (or outside) the deposition cavity12, as shown in FIG. 1, or alternatively in the form of flat Thermocoax™coils 42, as shown in FIG. 2. One of the possible configurations of theThermocoax™ bent coil used in FIGS. 1 and 2, is shown in FIG. 3 whichincludes Thermocoax™ winding having the length of the wire in eachsection of ˜950 mm and the diameter of the wire ˜2 mm.

Although the heating elements described herein are Thermocoax™ heatingelements, any suitable heating elements may be utilized. The Thermocoax™heating elements of the preferred embodiment are screened electricalresistance wires of small diameter designed to be shaped andincorporated into heating systems. They consist of one or two straightcurrent-carrying cores in a flexible metal sheath, electricallyinsulated from one another and from the sheath by means of a highlycompacted refractory powder. The core is generally a nickel-chromium80/20 composition, but may be formed or pure nickel, zirconium copper,or any other suitable materials. The insulator is generally a highlycompacted mineral powder, generally formed of magnesium oxide. Thesheath of the heating element may be formed of stainless steel or anyother suitable material for the particular thermal qualities of theheating element. Thermocoax™ is a product of Thermocoax of Cedex,France.

The cavity heater 42, which heats the walls 14 to the temperature T₁, isformed by, for example, three sections of Thermocoax™ meander-likeelements, with a diameter of the wire being ˜2 mm with a length of 300cm total, and a total resistance of 8.2 Ohm. With a maximum current of15 amps through the element 44, the maximum power generated is15²×8.2=1845 W. One exemplary geometry of one section of the Thermocoax™element 44 is shown in FIG. 3.

The non-contact heater 10 can be used for deposition of different filmson the substrate 22. For example, the system may be used for depositionof films of high temperature superconductor, such as Y—Ba₂—Cu₃—O_(x),which is a multicomponent material. This material requires a substratetemperature of ˜800° C. to grow in usable crystalline form. However,this material decomposes at temperatures above 900° C. As the allowabletemperature of the cavity wall 14 is limited to 900° C., the substratetemperature is limited to ˜750° C. Additional heating, which is neededin order to reach the substrate temperature ˜800° C., is provided by twocylindrical quartz halogen lamps placed off the deposition axis tominimize material deposit on the surfaces of the lamps. Cylindricalellipsoidally shaped reflectors 32, 34 provide coupling of the lampsradiation to the substrate 22. The lamps 28 and 30 are located in thefirst focus 36 of the reflectors 32 and 34, while the substrate 22 islocated near the second focus 38 of the reflectors 32, 34, as shown inFIGS. 1 and 2. The effective temperature of the lamps is ˜1200° C., andtheir power is ˜500 W, respectively.

The non-contact heater 10 of the present invention is adaptable for aparticularly important case of a tape-like substrate having a width of˜15 mm. In order to accommodate such a substrate, the shape of thedeposition cavity 12 is elongated, as best shown in FIGS. 4 and 6, witha slot-like opening 16 for deposition.

In FIG. 4, at least one elliptical cylinder reflector 32 (or 34) isattached to the wall 14 of the deposition cavity 12 so that theradiation emanating from the lamp 30 is delivered to the extendedtape-like substrate 22 through the radiation path to heat the substrateto the optimal temperature.

Although the non-contact heater of the present invention has beendescribed supra with reference to FIGS. 1, 2, and 4 as havingellipsoidal type reflector, it has to be understood that other types ofreflectors can be used in the arrangement of the present invention aswell. The function of the reflector is to direct the radiation emanatingfrom the radiation sources to the radiation paths formed in the cavitywall, so that the radiation could be delivered to the substrate forheating the same. For example, as shown in FIG. 5, the reflector can bearranged with a planar mirror 35 located behind the radiation source 28.In an alternative embodiment, shown in FIG. 6, the reflector may beformed as a cylindrical paraboloid 37. The radiation source will belocated with focus of the paraboloid. In this arrangement the radiationis well collected. The paraboloid reflector shown in FIG. 6 is adaptedfor heating of the extended tape-like substrate, where the paraboliccylinder 41 is attached to the elongated cavity heater 12.

The temperature of the substrate 22 is controlled by balancing the powerreceived from the source P_(in) and the power lost due to radiationescaping external the system P_(OUT); that is P_(IN)=P_(OUT) (T_(s)). Asthe radiation losses are proportional to the fourth power of absolutetemperature (P_(OUT)˜T⁴), a two times increase in total power P_(IN) iscapable of increasing the substrate temperature approximately2^(1/4)=1.2 times. A 2 inch long, cavity type heater with a power of1000 W provides substrate temperature T_(s)=700° C.=1000K. Thus,additional power of 1000 W from the remote source, with the two quartzhalogen lamps and elliptical reflectors shown in FIGS. 1 and 2, canincrease T_(s) to 1000K×1.2=1200K=900° C., which is sufficient fordeposition. The condition of T₁<T_(s)<T₂, where T_(s) is the substratetemperature, T₁ is the temperature of the housing wall 14, and T₂ is theeffective temperature of the source of radiation 28, 30, represents anoptimal thermal condition for depositing high quality films ofmulticomponent material on the substrate 22. The non-contactmeasurements of the temperature T_(s) of the substrate 22 wasaccomplished using infrared thermocouple detector (IR t/c.1x)manufactured by the Exergan Co. The non-contact measurements wereperformed using a measurement technique explained in detail infra withregard to FIGS. 7 and 8.

Due to the presence of the openings in the cavity wall, radiation ofenergy from the substrate via the openings results in a decrease of thesubstrate temperature T_(s), and establishes a temperature difference ofT₁=T_(s)+Δ. The temperature of the wall of a real cavity (as opposed toan ideal cavity) is always higher than the temperature of the substrate.Not only is this disadvantageous for the quality of grown films, it alsomay be a problem for measurement/control over the substrate temperature,which must be non-contact (via radiation) as well. Radiation received bya detector can include a significant portion coming from “background”objects (objects other than the substrate). Given that the temperatureof the cavity wall is greater (Δ) than that of the substrate, the“parasitic” radiation can reduce the control sensitivity, as well asselectivity and quality thereof. This follows from the fact that theradiation intensity R is a strong function (R˜T⁴) of absolutetemperature T, measured in K. Thus, even a small difference Δ intemperatures may result in a strong background radiation reading at thedetector coming from the wall. The wall contribution is especiallystrong if the substrate material is transparent to the wall radiation(Al₂O₃, as an example). In this case, the sensor would sense the wallradiation passing through the substrate.

In the present invention, this problem is solved by employing aspatially selective, non-contact temperature measurement technique inorder to reduce the undesirable contribution of the cavity wallradiation. A radiation receiver is placed in the plane of the substrateimage (created by the radiation capturing optics, a lens for example)and is sized to match the dimensions of the image of the substrate areachosen to be used for the sensing. In this manner, the contribution ofthe substrate radiation in the overall radiation received is maximizedand the noisy contribution of the radiation from the walls is minimized.

As shown in FIGS. 7 and 8, non-contact measurement of the substratetemperature may be accomplished using a temperature sensor (athermocouple, for example) 50 located outside the cavity 12 andoptically coupled to the substrate surface via a small hole (or holes)52 in the cavity wall 14.

FIGS. 7 and 8 illustrate the basic optical scheme of the measurementtechnique, where an area S on the substrate surface 22 is chosen to beused as a source of radiation for the sensing process. A lens 54 (madeof Ge, for example) picks up and transports the radiation from the areaS. In the plane P_(s) of the area image, created by the lens, theradiation will have the greatest density (concentration). Other sources(background objects such as the housing wall 14, for example), locatedfar from the substrate, will have their images in planes other thanP_(s). Accordingly, the density of their radiation in the plane P_(s)will be reduced. Thus, for the sensor 50 located in the plane P_(s), thetotal amount of picked-up radiation will have the greatest proportion(Radiation from substrate/Radiation from background) coming from thearea S.

The size of the sensor element 50 has to match the size of the imagefrom area S. In this manner, the sensor selectivity is improved, sinceit does not pick up radiation that comes from sources other than the Sarea. The field of view (FOV) of the optics should match the area Sselected. Thus the effect of background radiation is reduced as well.

By using a thermocouple directly attached to the substrate, sensorcalibration may be performed.

Referring specifically to FIG. 8, illustrating the design of the heaterof the present invention adapted for the strip-type substrate 56,radiation from a small area on the surface of the heated strip 56 exitsthe deposition cavity 12 via small openings 52, and is focused by lenses54 on the absorbing body of a thermocouple 50. The thermocoupletemperature is calibrated relative to the temperature of the surface ofthe strip-type substate 56. Field of view (FOV) of the lens is selectedto be limited to the small area on the strip (the thermocouple does not“sense” radiation coming from the cavity walls 14).

The measurements confirm that the non-contact heater of the presentinvention, which includes the semi-open cavity 12 having a walltemperature T₁ below the temperature of material deposition (T₁<T_(d))in combination with at least one additional remote source of radiation,which has the effective temperature T₂>T₁ and is coupled to thesubstrate via the radiation delivery optics, provides the temperaturecondition of T₁<T_(s)<T₂, which is required for multi-componentmaterials deposition as well as stability and uniformity of substrateheating.

Although this invention has been described in connection with specificforms and embodiments thereof, it will be appreciated that variousmodifications other than those discussed above may be resorted towithout departing from the spirit or scope of the invention as definedin the appended claims. For example, equivalent elements may besubstituted for those specifically shown and described, certain featuresmay be used independently of other features, and in certain cases,particular locations of elements may be reversed or interposed, allwithout departing from the spirit or scope of the invention as definedin the appended claims.

1. A non-contact heater for heating an object, comprising: a first housing having a housing wall defining and enveloping an internal cavity of said first housing, said housing wall being heated to a temperature T₁ and having at least one radiation path formed therein; and at least one source of radiation with a predetermined effective temperature T₂ positioned external to said internal cavity of said first housing; wherein the radiation emanating from said at least one source of radiation is delivered to an object positioned in said internal cavity through said at least one radiation path to heat the object to a temperature T_(s), so that T₁<T_(s)<T₂, wherein T₁ is the temperature of said housing wall, T₂ is the predetermined effective temperature of said at least one source of radiation, and T_(s) is the temperature of the object.
 2. The non-contact heater of claim 1, further comprising reflector means optically coupled to said at least one source of radiation.
 3. The non-contact heater of claim 2, wherein said reflector means is for directing the radiation emanating from said at least one source of radiation to said at least one radiation path formed in said housing wall.
 4. The non-contact heater of claim 2, wherein said reflector means includes at least one second housing attached to said housing wall of said first housing, said at least one second housing having an internal surface forming an ellipsoidal reflector with a first focus positioned outside said internal cavity and with a second focus positioned in said internal cavity, wherein said at least one source of radiation is positioned in said first focus of said ellipsoid reflector, the object is positioned in said internal cavity in proximity to said second focus of said ellipsoid reflector, and said at least one radiation path is positioned on a main focal axis of said ellipsoid reflector connecting said first and second focuses thereof.
 5. The non-contact heater of claim 4, wherein said at least one second housing is shaped as an elliptical cylinder.
 6. The non-contact heater of claim 2, wherein said reflector means includes at least one planar mirror located behind said at least one source of radiation.
 7. The non-contact heater of claim 2, wherein said reflector means includes a reflective surface shaped to concentrate the radiation emanating from said at least one source of radiation on said at least one radiation path.
 8. The non-contact heater of claim 2, wherein said reflector means includes a reflective surface shaped as a cylindrical paraboloid, said at least one source of radiation being positioned in the focus of said cylindrical paraboloid.
 9. The non-contact heater of claim 8, wherein said reflector means further includes at least one reflector housing, said at least one reflector housing having an internal surface defining said reflective surface formed as said cylindrical paraboloid.
 10. The non-contact heater of claim 1, wherein said object is a substrate for material deposition, and wherein said intemal cavity is a deposition cavity, said housing wall further having a flux opening aligned with a deposition flux emanating from a deposition source disposed remotely from said deposition cavity to allow coupling between the deposition flux and the substrate mounted in said deposition cavity.
 11. The non-contact heater of claim 1, further comprising a heating element thermally coupled to said housing wall to heat the housing wall to the temperature T₁.
 12. The non-contact heater of claim 1, wherein said at least one source of radiation is a source of optical radiation.
 13. The non-contact heater of claim 1, wherein said at least one source of radiation includes a quartz halogen lamp.
 14. The non-contact heater of claim 10, further comprising an additional source of radiation mounted remotely from said deposition cavity and optically coupled to the substrate.
 15. The non-contact heater of claim 14, wherein said housing wall further has an additional radiation path formed therein to provide radiation coupling between said additional source of radiation and the substrate.
 16. The non-contact heater of claim 10, wherein said at least one source of radiation is positioned off-axis of said deposition flux.
 17. The non-contact heater of claim 11, wherein said heating element includes at least one heater winding attached to said housing wall of said first housing.
 18. The non-contact heater of claim 10, further comprising a deposition screen mounted in proximity to said at least one radiation path to prevent deposition of a material thereon. 